Apparatus and method for melting and dispensing thermoplastic material

ABSTRACT

An apparatus for melting thermoplastic material is disclosed. The apparatus includes a heated manifold and at least one heating element disposed within the heated manifold. The heated manifold defines a plurality of cavities, a pump supply passage, and a discharge passage. The plurality of cavities are spaced apart from one another, and each receives particles of thermoplastic material from a hopper. The particles of thermoplastic material are melted within the plurality of cavities. The pump supply passage receives molten thermoplastic material from the plurality of cavities and supplies the molten thermoplastic material to a pump. The discharge passage receives pressurized molten thermoplastic material from the pump and is in fluid communication with a dispenser. The heating element transfers heat substantially throughout the heated manifold.

CROSS-REFERENCES

This application is a continuation of U.S. patent application Ser. No.15/218,059, filed Jul. 24, 2016, and published as U.S. Patent App. Pub.No. 2016/0332335, which is a divisional of U.S. patent application Ser.No. 14/021,424, filed Sep. 9, 2013, and issued as U.S. Pat. No.9,427,766 on Aug. 30, 2016, which is a continuation of U.S. patentapplication Ser. No. 13/494,124, filed Jun. 12, 2012, and published asU.S. Patent App. Pub. No. 2012/0247665 on Oct. 4, 2012, which is adivisional of U.S. patent application Ser. No. 12/158,756, filed Jun.23, 2008, and issued as U.S. Pat. No. 8,201,717 on Jun. 19, 2012, whichclaims priority to International Patent App. No. PCT/US2007/060569,filed Jan. 16, 2007, which claims the benefit of U.S. Provisional PatentApp. No. 60/759,305, filed Jan. 17, 2006, the disclosures of which areincorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates to apparatuses and methods for melting anddispensing thermoplastic materials.

BACKGROUND

Thermoplastic materials include those materials that can be repeatedlymelted and cooled to a solid. Thermoplastic material includes waxes andthermoplastic adhesives, also referred to as “hot melt” adhesives, etc.“Hot melt” adhesives are used in a wide variety of applicationsincluding the assembly of various types of products including furniture,doors, windows, etc., and the closing of boxes, containers, etc.

Typically, solid hot melt adhesive, in various shapes and sizes, issupplied to a melter that includes a heated tank and/or a heated grid toproduce molten hot melt adhesive. Solid hot melt adhesive can also besupplied in drums or barrels in which the adhesive is melted by the useof a platen. After heating, the molten adhesive is pumped through aheated hose, to maintain the molten material at the required applicationtemperature, to an applicator or dispenser, sometimes referred to as adispensing “gun” or gun, or a gun module, comprising a valve and anozzle. Heated hoses are believed to be a primary source of charringproblems associated with hot melt adhesives, particularly in systemsrequiring relatively low melt rates. In such applications, the residencetime of the molten adhesive within a heated hose can exceed the “potlife” of the adhesive as a result of the relatively high volume ofmolten adhesive within the hose and the relatively low usage rate. “Potlife” as used herein is the maximum time at the system temperaturebefore the adhesive starts to degrade resulting in increased viscosityand charring. Oversized tanks or other reservoirs of molten adhesive canalso contribute to this problem. Exceeding the “pot life” of athermoplastic adhesive may result in operational problems, such asfilter clogging, and the cleaning required after charring has occurred.

It is desirable to provide an adhesive dispensing system that reducescharring. It may also be desirable to provide an adhesive dispensingsystem where the time the material is maintained at elevated temperatureis significantly reduced and/or the volume of material is reduced.Finally, it may also be desirable to eliminate the need of heated hosesfor transporting liquefied hot melt.

SUMMARY

According to a first aspect of the present invention, an apparatus isprovided for melting and dispensing thermoplastic material that may be ahot melt adhesive. The apparatus includes an un-heated hopper having aninlet for receiving particles of a thermoplastic material and an outletfor discharging the particles and a heated manifold including at leastone cavity formed therein. The at least one cavity has an inletcommunicating with the outlet of the hopper for receipt of the particlesof the thermoplastic material from the hopper. The hopper is disposedexternal of the heated manifold. The at least one cavity furtherincludes an outlet. The heated manifold is effective for melting theparticles into molten thermoplastic material therein. The apparatusfurther includes a pump having an inlet and an outlet, with the inlet ofthe pump being in fluid communication with the outlet of the at leastone cavity. The apparatus also includes a dispenser having an inlet andan outlet. The outlet of the pump is in fluid communication with theinlet of the dispenser, and the outlet of the dispenser is effective fordispensing the molten thermoplastic material therethrough.

Various embodiments of the apparatus of the present invention can alsoinclude one or more of the following features. For instance, both thepump and dispenser can be mounted on the manifold. The manifold caninclude a plurality of cavities formed in the manifold, with thecavities spaced apart from one another and each cavity having an inletcommunicating with the outlet of the hopper and an outlet. A collectorpassage can be fluidicly coupled with the outlet of each of thecavities. The collector passage includes an outlet in fluidcommunication with the inlet of the pump.

The hopper can be made of a polymeric material. A plurality of thecavities can be formed in the heated manifold, with the cavities spacedapart from one another and each having an inlet communicating with theoutlet of the hopper and further including an outlet. In thisembodiment, the collector passage can be in fluid communication with theoutlet of each of the cavities.

The apparatus can further include a plurality of fins, with each of thefins being disposed intermediate of two adjacent ones of the cavities.In one embodiment, the fins have a triangular-shaped cross-section, withan apex disposed within the outlet of the hopper.

The apparatus can further include an un-heated hose coupled at one endto the inlet of the hopper and having an opposite end effective forreceiving the particles of the thermoplastic material therethrough. Moreparticularly, the opposite end of the hose is operatively coupled to asource of pressurized air whereby the opposite end of the hose iseffective for suctioning the particles of the thermoplastic materialfrom a supply reservoir of the particles. The hose is effective fortransporting the particles to the inlet of the hopper when thepressurized air is flowing within the hose. In this embodiment, thehopper includes an upper portion comprising the inlet of the hopper andfurther comprises a plurality of apertures formed therein and disposedabout a periphery thereof. The apertures are effective for exhaustingpressurized air entering the hopper from the un-heated hose.

The apparatus can further include a device effective for moving theparticles of the thermoplastic material adhesive around and along thelongitudinal axis of the hopper and through the outlet of the hopper.The device can be an auger with a blade having a major diameter whichcan be either substantially constant or tapered. A motor can bedrivingly coupled with the auger.

According to a second aspect of the present invention, a method isprovided for melting and dispensing thermoplastic material, comprisingsupplying particles of a thermoplastic material to an un-heated hopperdisposed external of a heated manifold, discharging the particles of thethermoplastic material from the hopper into the heated manifold, meltingthe particles of the thermoplastic material into molten thermoplasticmaterial within the heated manifold, directing the molten thermoplasticmaterial through the heated manifold to a dispenser mounted on themanifold, and dispensing the molten thermoplastic material from thedispenser onto a workpiece.

In other embodiments, the method can also comprise one or more of thefollowing features. The particles of thermoplastic material can betransported from a supply reservoir of the particles, through anun-heated hose and to the inlet of the hopper. The particles can bedischarged from the hopper into the heated manifold solely by gravity. Apre-determined level of the particles within the hopper can beautomatically maintained, and the hopper can be mounted on the heatedmanifold.

According to an alternative embodiment, a method is provided comprisingsupplying particles of a thermoplastic material to an un-heated hopperhaving an outlet and a longitudinal axis, with the hopper being disposedexternal of a heated manifold and moving the particles around and alongthe longitudinal axis of the hopper to discharge the particles throughthe outlet of the hopper and into the heated manifold. The methodfurther comprises melting the particles into molten thermoplasticmaterial within the heated manifold, directing the molten thermoplasticmaterial through the heated manifold to a dispenser mounted on themanifold, and dispensing the molten thermoplastic material from thedispenser.

In various embodiments, the method can further comprise one or more ofthe following features. The particles can be moved around and along thelongitudinal axis by an auger disposed within the hopper. The moltenthermoplastic material can be directed through the heated manifold to apump mounted on the manifold and pumped from the pump through themanifold to the dispenser.

According to a third aspect of the present invention a method isprovided for bonding two members of a window sash to one another tocreate a corner of the window sash, with the two members being disposedin abutting relationship with one another. The method comprises mountingan apparatus for melting and dispensing a hot melt adhesive on adedicated automation device, with the apparatus comprising a heatedmanifold, an un-heated hopper disposed external of and mounted on theheated manifold, a pump mounted on the heated manifold and a dispensermounted on the heated manifold. The method further comprises supplyingparticles of a hot melt adhesive to the un-heated hopper and dischargingthe particles of the hot melt adhesive from the hopper into the heatedmanifold. The method also comprises melting the particles of the hotmelt adhesive into molten hot melt adhesive within the heated manifold,directing the hot melt adhesive through the heated manifold to thedispenser and aligning the dispenser with an aperture formed in a firstone of the two members of the window sash, with the aperture being influid communication with a first channel extending between the interiorof the first member of the window sash and the interior of the secondmember of the window sash. The method further comprises injecting themolten hot melt adhesive from the dispenser into and through theaperture into the first channel.

According to a fourth aspect of the present invention, a method isprovided for bonding two ends of a filter to one another, the filterbeing formed into a cylindrical shape with the two ends of the filterbeing disposed in abutting relationship with one another. The methodcomprises mounting an apparatus for melting and dispensing a hot meltadhesive on a dedicated automation device, the apparatus comprising aheated manifold, an un-heated hopper disposed external of and mounted onthe heated manifold, a pump mounted on the heated manifold and adispenser mounted on the heated manifold. The method further comprisessupplying particles of a hot melt adhesive to the un-heated hopper,discharging the particles of the hot melt adhesive from the hopper intothe heated manifold, melting the particles of the hot melt adhesive intomolten hot melt adhesive within the heated manifold and directing themolten hot melt adhesive through the heated manifold to the dispenser.The method also comprises aligning the dispenser with the two ends ofthe filter and dispensing the molten hot melt adhesive between the twoends of the filter to form a seam bonding the two ends together.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims and accompanying drawings wherein:

FIG. 1 is an isometric view of an apparatus for melting and dispensingthermoplastic material according to the present invention;

FIG. 2 is an isometric view similar to FIG. 1 but with the includedhopper shown in exploded assembly view to further illustrate theincluded heated manifold;

FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 2;

FIG. 5 is a cross-sectional view similar to FIG. 3 illustrating analternative embodiment of an apparatus for melting and dispensingthermoplastic material according to the present invention;

FIG. 6 is a cross-sectional view similar to FIG. 5 illustrating anotheralternative embodiment of an apparatus for melting and dispensingthermoplastic material according to the present invention;

FIG. 7 is a plan view of a window including a window sash;

FIG. 8 is an enlarged view of the area circled in FIG. 7 furtherillustrating one of the corners of the window, illustrating oneapplication of the apparatus of the present invention;

FIG. 9 is an isometric view of a filter illustrating another applicationof the apparatus of the present invention;

FIG. 10 is an enlarged, fragmentary schematic representation of aportion of the filter shown in FIG. 9; and

FIG. 11 is a perspective view illustrating one application of theapparatus of the present invention.

DETAILED DESCRIPTION

Referring now to FIG. 1 and FIG. 3, an apparatus 10 for melting anddispensing thermoplastic material such as hot melt adhesives isillustrated. Although apparatus 10 can be used to dispense variousthermoplastic materials, it is particularly advantageous when used todispense hot melt adhesive, and the apparatus 10 will be describedherein in conjunction with this application. Apparatus 10 includes ahopper 12 having an inlet 14 (shown in FIG. 3) effective for receivingsolid particles of a hot melt adhesive, such as in pellets or chicklets,from a supply reservoir or tank 16. In the illustrative embodiment, thesolid particles of the hot melt adhesive are supplied to the inlet 14 ofhopper 12 by an automatic feed system 18 such as the FillEasy™ AdhesiveFeed System or the Fillmaster® Adhesive Feed System, both made by theNordson Corporation. As used herein the term “solid particles” refers toparticles that are in the solid state, not the liquid or molten state.However, as may be appreciated by one skilled in the art, solidparticles can have varying degrees of hardness depending upon factorssuch as exposure to atmosphere, for example. Accordingly, some solidparticles may be somewhat “soft to the touch”. The automatic feed system18 includes an un-heated transport hose 20 coupled at one end 20 a tothe inlet 14 of hopper 12 and terminating at an opposite end in asuction wand 22. A source of pressurized air 24 is supplied to thesuction wand 22 via one or more conduits 26. More particularly, thepressurized air is supplied to a venturi pump (not shown) containedwithin the suction wand 22. The suction wand 22 is disposed proximatethe inlet of the supply reservoir 16 of the solid particles of the hotmelt adhesive and the venturi pump included in the suction wand iseffective for suctioning the solid particles of the hot melt adhesiveout of supply reservoir 16 and into hose 20, and for transporting orpumping the solid particles of the hot melt adhesive through hose 20 tothe inlet 14 of hopper 12 via pressurized air.

Alternatively, a screw conveyor or other transport system can be used totransport the solid particles of the hot melt adhesive from supply tank16 to the inlet 14 of hopper 12. As a further alternative, the automaticadhesive supply system 18 can be omitted, with the solid particles ofthe hot melt adhesive being manually fed into the inlet 14 of the hopper12. In this case, the hopper can include a lid, which can be opened formanual supply of the particles into the hopper 12 and be otherwiseclosed.

In the illustrative embodiment shown in FIG. 1, the hopper includes alower portion 28, intermediate portion 30 and upper portion 32. Theupper portion 32 is a hollow cylinder which is suitable for acceptinghose 20. The upper portion 32 includes a plurality of apertures 34formed therein and disposed about a periphery of the upper portion 32.Each of the apertures 34 communicates with an interior chamber 36 (FIG.3) formed by the upper portion 32 of hopper 12 and open onto an exteriorsurface 38 of the upper portion 32. Accordingly, apertures 34 areeffective for exhausting pressurized air entering chamber 36 from thehose 20, to the atmosphere exterior of hopper 12.

Apparatus 10 includes a heated manifold 40 and hopper 12 may be mountedto manifold 40 or closely coupled thereto. The lower portion 28 ofhopper 12 includes a peripheral flange 42 that is disposed in contactingengagement with manifold 40. A clamp 44, made of an insulating material,is configured to receive the peripheral flange 42 and is used to mountthe hopper 12 on manifold 40. The clamp 44 may be secured by a pluralityof conventional fasteners, such as bolts 46 (FIG. 1), which pass throughapertures (not shown) formed in the clamp 44 and into mating apertures48 formed in the manifold 40, as best appreciated with reference to theexploded assembly view shown in FIG. 2. The insulated clamp 44 iseffective for maintaining the peripheral flange 42 of the hopper 12 atan acceptable temperature. Flange 42, as well as the remainder of hopper12 can be made of an insulating material. For example, hopper 12 can bemade of a polymeric material having a relatively low thermalconductivity such as polytetrafluoroethylene, commonly referred to asTeflon®. In contrast, the manifold 40 is made of a metal having arelatively high coefficient of conductive heat transfer, such asaluminum.

With reference to FIGS. 1 and 2, the periphery of the intermediateportion 30 of hopper 12 may have an irregular shape that includes twosurfaces 50 that may be concave as shown. Alternatively, surfaces 50 maybe substantially flat-machined surfaces. A hole can be formed in andextend through the intermediate portion 30 of hopper 12 such that oneend of the hole opens onto an interior chamber 52 (FIG. 3) that isdefined by the lower 28 and intermediate 30 portions of hopper 12. Theopposite end of the hole opens onto one of the concave surfaces 50 ofthe intermediate portion 30 of hopper 12. A level sensor 54 can extendthrough the aperture formed in the intermediate portion 30 such that adistal end of the level sensor 54 is disposed within the interiorchamber 52. The distal end of the sensor 54 can be substantially flushwith an inner surface 58 of hopper 12. When the level of the solidparticles 56 of hot melt adhesive falls below the level sensor 54, thesensor 54 can send a signal to a controller (not shown) that controlsthe adhesive supply system 18 such that additional hot melt adhesive istransported from the supply reservoir 16 through hose 18 into hopper 12.

The opening in the bottom of hopper 12 can be larger than the opening inthe top of hopper 12, such that the inner surface 58 of hopper 12 formsa relatively small angle 60, such as about 5°, with the vertical. Thisflared surface 58 facilitates movement of the particles 56 of the hotmelt adhesive through hopper 12.

A plurality of heating elements 62 are disposed within manifold 40 andextend substantially therethrough as illustrated in FIGS. 3 and 4. Inthe illustrative embodiment, each of the heating elements 62 areelectrical resistance heating elements. An electrical cord set 63 isprovided that is electrically coupled to heating elements 62 and can becoupled to a source of electricity (not shown). Heating elements 62 areeffective for transferring heat substantially throughout the manifold 40via conduction. The particular positioning of heating elements 62 withinmanifold 40 will be discussed in greater detail subsequently.

A plurality of cavities 64 can be formed in manifold 40 and spaced apartfrom one another. Each of the cavities 64 includes an inlet 66 (FIG. 4)that communicates with an outlet 68 (FIG. 3) of hopper 12. Accordingly,the solid particles 56 of the hot melt adhesive are free to drop intothe cavities 64 under the action of gravity. The inlets 66 of thecavities 64 open onto an upper surface 70 of manifold 40. Manifold 40further includes a plurality of fins 72 that protrude upwardly fromsurface 70 and extend into the outlet 68 of hopper 12. Each of the fins72 can have a triangular-shaped cross-section with a sharp, upwardlypointing apex 74 at the interface of two sides of the triangular shapeof the fins 72. The triangular shape of fins 72 helps guide the adhesiveinto cavities 64 and ensures that the solid particles are not impededfrom entering cavities 64. Additionally, the triangular shape of fins 72provides increased surface area, relative to fins having a rectangularcross-section for instance, which is advantageous with respect to heattransfer to the adhesive. Since the hopper 12 is un-heated it remains atambient temperature with the exception of the lowermost portion whichreceives heat transfer from the heated manifold 40.

Melting occurs within cavities 64 and transforms the solid particlesinto molten, hot melt adhesive, by the time the material discharges fromcavities 64. Each of the cavities 64 includes an outlet 76 proximate thebottom of the corresponding cavity 64. Each of the outlets 76 are influid communication with a collector passage 78 formed in manifold 40.The molten hot melt adhesive discharges from the collector passage 78through an outlet 80 to a pump supply passage 82. The pump supplypassage 82 is in fluid communication at one end with the outlet 80 ofthe collector passage 78, and therefore with each of the cavities 64,and is in fluid communication at the opposite end with an inlet 84 of apump 86. As shown in FIG. 3, the pump supply passage 82 slopesdownwardly from outlet 80 to pump inlet 84 so the adhesive can flow topump inlet 84 under the force of gravity.

In the illustrative embodiment of FIGS. 1-4, the pump 86 is a meteredgear pump that is drivingly coupled with a motor 88, via a drivetrainindicated generally at 90. The motor 88 can be a servo motor and thedrivetrain 90 can include a gear box 92 receiving a rotatable outputshaft (not shown) of the motor 88 and a coupling 94 disposed between thegear box 92 and the pump 86. The motor 88 and associated drivetraincontrol the speed of pump 86. Pump 86 may be mounted on manifold 40. Inthe illustrative embodiment, pump 86 is attached to manifold 40 byconventional fasteners such as bolts 87 which pass through a housing ofpump 86 and into manifold 40. Alternatively, other pumps could beutilized, including piston pumps.

A cover 97 is optionally provided that covers motor 86 and a portion ofdrivetrain 90. A bracket 96 can be disposed in surrounding relationshipwith a portion of the drivetrain 90 and can be used to mount apparatus10 to a portion of an overall system for dispensing hot melt adhesivethat can be a stationary structure or a dedicated automation device.

The molten hot melt adhesive discharges from pump 86 through outlet 98into a pump discharge passage 100 that is in fluid communication at anopposite end with an inlet 102 of a dispenser 104. Dispenser 104 may bemounted directly on manifold 40. A pressure transducer 106 can bedisposed in manifold 40 in fluid communication with the pump dischargepassage 100 so that it is effective for measuring the pressure of themolten hot melt adhesive discharging from pump 86. Pressure transducer106 can be electrically coupled to a control panel (not shown) and canprovide an annunciation or alarm signal to an operator controllingapparatus 10 which advises the operator that the pump discharge pressureof the molten adhesive is outside of the desired operating range.Apparatus 10 can include a filter 108 disposed in the pump dischargepassage 100 to filter fine particles of solid material that may existwithin the molten adhesive.

A suitable dispenser 104 is the model AG-900 gun module made by theNordson Corporation, which is a pneumatically operated module. However,a wide variety of other pneumatically or electrically operated guns canalso be used that are made by Nordson Corporation for extruding orpotentially fiberizing hot melt adhesive. In the illustrativeembodiments, a source of pressurized air (not shown) is supplied to asolenoid valve 110 (FIG. 1), which can comprise a conventional 4-waysolenoid valve. The dispenser 104 can include a pneumatically actuated,reciprocating piston element 112 that includes a disk 114 and a stem 116integral with disk 114. The piston element 112 can be biased in a closedposition via spring 118 such that the stem 116 is disposed against valveseat 120, thereby closing an outlet 122 of the gun 104.

A conduit 124, such as tubing, interconnects a port 126 on solenoidvalve 110 with a port 128 on the dispenser 104. Another conduit 130interconnects a port 132 on solenoid valve 110 with a port 134 ondispenser 104. Port 134 is in fluid communication with an internalcavity 136 disposed proximate one side of the disk 114 and port 128 isin fluid communication with an internal cavity 138 disposed proximate anopposite side of the disk 114. Accordingly, when an operator wishes toopen the dispenser 104, such that molten hot melt adhesive can dischargethrough outlet 122, the solenoid valve 110 is operated to providepressurized air to the internal cavity 138 and simultaneously ventcavity 136, such that a force is exerted on disk 114 that overcomes thebiasing force of spring 118 and lifts the reciprocating piston element112 off of valve seat 120, thereby opening the dispenser 104. When anoperator wishes to close the dispenser 104, pressurized air is suppliedto cavity 136, while cavity 138 is simultaneously vented, via solenoidvalve 110.

FIG. 5 illustrates an apparatus 150 for melting and dispensing hot meltadhesive according to an alternative embodiment of the presentinvention. Apparatus 150 is the same as apparatus 10 with the followingexceptions. Apparatus 10 includes a rotatable auger 152 disposed withina hopper 151. Both hopper 151 and auger 152 can be made of an insulatingmaterial. For example, a polymeric material having a relatively lowthermal conductivity such as polytetrafluoroethylene, commonly referredto as Teflon®, can be used. The auger 152 includes a shaft 154 and ahelical blade 156 integral with the shaft 154. The blade 156 has a majordiameter 158 that is substantially constant throughout the longitudinallength of the auger 152. Accordingly, auger 152 is considered to be astraight auger. Auger 152 is drivingly coupled with a motor 160 and,more particularly, a rotating output shaft 162 of motor 160 is drivinglycoupled with the shaft 154 of auger 152. A gear box (not shown) andcoupling (not shown) may be interposed between motor 160, which can bean electric motor, and auger 152 as required. Alternatively, auger 152can be driven by a pneumatic device. The auger 152 is effective formoving the solid particles of the hot melt adhesive around and along alongitudinal axis 159 of hopper 151 and through outlet 163 of hopper 151into cavities 64.

The auger 152 is sized and configured with an appropriate pitch suchthat the feed rate of the solid particles 56 into cavities 64 is greaterthan the melt rate of particles 56 within cavities 64. This produces adesired back pressure on the hot melt adhesive within cavities 64 toincrease the melt rate and fluid momentum as it is dispensed. Hopper 151includes a side mounted inlet port 164 formed therein and including aninlet 166 effective for receiving the solid particles 56 of hot meltadhesive therethrough. The hose 20 of the adhesive supply system 18 canbe coupled to the inlet port 164 and communicates with inlet 166. Aplurality of apertures 168 are formed in the inlet port 164 and areeffective for exhausting pressurized air entering the inlet port 164from hose 20, in the same manner as discussed previously with respect toapertures 34 of apparatus 10. Hopper 151 has a lower portion 170 with aperipheral flange 172 that are the same as the lower portion 28 andperipheral flange 42 of apparatus 10. Hopper 151 further includes anupper portion 174 that includes the inlet port 164. A level sensor suchas the previously discussed sensor 54 (not shown in FIG. 5) can bedisposed in the upper portion 174 such that a distal end of the levelsensor is disposed within an interior chamber 176 of hopper 151. Theremaining features and functions of apparatus 150 are the same asapparatus 10 discussed previously.

In another alternative embodiment, the pump 86, motor 88 and drivetrain90 can be omitted from apparatus 150. In this case, the outlet (notshown in FIG. 5) of the collector passage 78 is in fluid communicationwith the inlet 102 of the dispenser 104. Pressure transducer 106 andfilter 108 can also be included in this embodiment.

FIG. 6 illustrates another apparatus 200 for melting and dispensing hotmelt adhesive according to the present invention. In this embodiment,auger 152 is replaced with an auger 202 having a shaft 204 and a helicalblade 206 integral with the shaft 204. As with auger 152, auger 202 canbe made of an insulating material. For example, a polymeric materialhaving a relatively low thermal conductivity such aspolytetrafluoroethylene, commonly referred to as Teflon®, can be used.The blade 206 includes a major diameter 208 that is tapered outwardlyfrom top to bottom and accordingly, auger 202 is considered to be atapered auger. The structural features and functions of apparatus 200are otherwise the same as apparatus 150. Since the major diameter 208 ofblade 206 is smaller proximate the inlet port 164, additional space isprovided to receive the solid particles 56 of hot melt adhesive.

During operation of apparatus 10, feed system 18 automatically maintainsa pre-determined level of the solid particles 56 of the hot meltadhesive within hopper 12 based on feedback provided by level sensor 54.The feed system 18 may operate independently of the operation of motor88, pump 86 and dispenser 104. A controller (not shown), which can be aprogrammable logic controller for instance, associated with a parentmachine, such as the subsequently discussed dedicated automation device300 illustrated schematically in FIG. 11, sends an “ON” signal to thecontroller (not shown), such as a programmable logic controller,associated with motor 88 and dispenser 104 when it is desired todispense the molten or fluid hot melt adhesive out of dispenser 104.This controller then sends synchronized signals to motor 88, to start,and to the solenoid valve 110 causing dispenser 104 to open. Thesesignals can be synchronized so that dispenser 104 is opened before motor88 and pump 86 are turned on to avoid damage to dispenser 104 that couldoccur if motor 88 and pump 86 would be turned on before dispenser 104 isopened. One or more time delay relays can be used to synchronize openingdispenser 104 and then turning on motor 88 and pump 86. The molten hotmelt adhesive is then discharged from dispenser 104 onto a workpiece,for example the window sash 256 illustrated in FIGS. 7 and 8 or thefilter 290 illustrated in FIGS. 9 and 10.

The operation of apparatus 150 and apparatus 200 are the same asapparatus 10, when pump 86, motor 88 and drivetrain 90 are included,except that the included augers 152 and 202, respectively, force theparticles 56 out of hopper 151, instead of the particles dischargingfrom hopper 151 solely by gravity as is the case with hopper 12 ofapparatus 10.

The apparatuses 10, 150 and 200 of the present invention can be used ina wide variety of applications, with the use of these apparatuses beingparticularly advantageous in those applications having relatively lowdispense or discharge rates, for example dispense rates of about 1 lb/hrof hot melt adhesive. Apparatus 10 minimizes the “residence time” of thehot melt adhesive within apparatus 10 prior to dispensing the hot meltadhesive from dispenser 104. More particularly, the “residence time” ofthe hot melt adhesive within apparatus 10 is less than the pot life ofthe hot melt adhesive, thereby at least minimizing charring problemsassociated with the hot melt adhesive. As used herein, “residence time”is the time the hot melt adhesive is in a molten state.

The following features of apparatus 10 contribute to the minimization ofresidence time of the hot melt adhesive within apparatus 10. Hopper 12is un-heated and may be made of a material having a relatively lowthermal conductivity, i.e., a material having a relatively lowcoefficient of conductive heat transfer. Further, the hopper 12 isdisposed external of heated manifold 40. Although hopper 12 may bemounted on heated manifold 40, the clamp 44, which is made of aninsulating material, may be used to receive the peripheral flange 42 ofhopper 12 to mount hopper 12 on heated manifold 40 and to discourageheat transfer from the heated manifold 40 to hopper 12. As a result ofthe foregoing, the hot melt adhesive within hopper 12 is generally notmelted and remains in a solid state (although some softening may occur).The solid hot melt adhesive, such as particles 56, is discharged intomanifold 40 on an “on-demand” basis in response to dispensing the moltenhot melt adhesive from dispenser 104.

The total combined volume of all of the cavities 64 and the heatingcapacity of heating elements 62 are selected so that the melt rate ofheated manifold 40 is greater than, but relatively close to, thedispense rate of the hot melt adhesive. For example, in one embodimentapparatus 10 may have a dispense rate of about 1 lb/hr and the melt rateof manifold 40 may be about 2 lbs/hr to about 4 lbs/hr. When a meteredgear pump is used, such as pump 86, a precise metered amount of moltenthermoplastic material discharges from pump 86 and flows through pumpdischarge passage 100 to the inlet 102 of dispenser 104. In view of theforegoing dispense and melt rates, hopper 12 may be relatively small.For example, in one embodiment hopper 12 may have an overall length ofabout eight inches and may have an inside diameter of about one to twoinches within the intermediate portion 30 of hopper 12. Inner surface 58may be tapered as discussed previously. Therefore, the inside diametermay vary somewhat within the intermediate portion 30 of hopper 12 andthe lower portion 28 of hopper 12. The maximum outside dimension of theintermediate portion 30 varies with the corresponding inside diameterand therefore may be about two to three inches, for example.Accordingly, apparatus 10 more closely approximates an ideal goal of“melting upon demand”, as compared to various conventional hot meltdispensing systems having melt rates which can significantly exceed, forexample, by an order of magnitude or more, the associated dispense rate.

Dispenser 104 is closely coupled to the heated manifold 40 and may bemounted on manifold 40. This results in essentially achieving melting atthe point of application, i.e., where the molten hot melt adhesive isdispensed onto a workpiece. Accordingly, the necessity of having aheated hose extending between a heated manifold or other heatedreservoir and an associated, remotely mounted dispenser, is eliminatedby the use of apparatus 10.

FIGS. 7, 8 and 11 illustrate one low dispense rate application where theapparatus of the present invention, such as apparatus 10, 150 or 200,can be used to strengthen the corner joint bonding of pultruded windows.FIG. 7 illustrates a window 250 having a frame 252 that can be mountedto a wall of a structure (not shown) and a pane of glass 254 secured bya window sash 256, which in turn is secured to the window frame 252.

Windows can be made of various materials with the window corner memberssecured to one another using different methods. For example, cornermembers of vinyl windows may be welded, corner members of aluminumwindows may be mechanically fastened and corner members of wood windowsmay be joined using adhesive or mechanical fasteners. Pultruded windowcorners, i.e., corners of windows constructed of a fiber-reinforcedcomposite, such as corner 258 of window sash 256 illustrated in FIG. 8,are bonded with an adhesive, such as a hot melt adhesive.

Pultruded window corners, such as corner 258, include an inner coreconstructed of composite wood or fiberglass. Wood veneer or vinylprofiles are laminated to the inner core. The structural integrity ofthe corner, such as corner 258, is critical and this structuralintegrity can be achieved by injecting the corner 258 with hot meltadhesive as follows.

The corner 258 joins a vertical member 260 of sash 256 with a horizontalmember 262 which are placed in abutting relationship with one anotherand then bonded together. As shown in FIG. 8, vertical member 260includes an aperture 264 that extends from the outer surface of member260 into the interior of member 260. Aperture 264 is in fluidcommunication with a channel 266, located in the interior of member 260,and a channel 268 formed in the interior of member 260 and extendinginto the interior of member 262. While channels 266 and 268 are shown asforming a 90° angle therebetween, they can be formed at different anglesrelative to one another and different numbers of channels can emanatefrom aperture 264. Other configurations and combinations of variousnumbers of apertures and channels may also be used. Sash 256 includestwo of the vertical members 260, two of the horizontal members 262 andfour corners 258, each formed by joining one of the vertical members 260to one of the horizontal members 262. Each of the corners 258 mayinclude the aperture 264 and channels 266 and 268, orientedappropriately for the particular corner 258.

The heated manifold 40, hopper 12, pump 86 and dispenser 104 ofapparatus 10, 150 or 200 may be mounted on the dedicated automationdevice 300, illustrated schematically in FIG. 11. Mounting hopper 12,pump 86 and dispenser 104 on heated manifold 40 provides a compact unitthat minimizes the space required to mount these components on adedicated automation device such as device 300. The space required isfurther minimized due to the relatively small size of hopper 10 andheated manifold 40 as compared to some conventional systems havingrelatively large tanks or other reservoirs of molten thermoplasticmaterial. This is illustrated schematically in FIG. 11 for apparatus 10,with the un-heated hose 20 coupled to hopper 12 as discussed previously.After aligning dispenser 104 with aperture 264 formed in the verticalmember 260 of window sash 256, the molten hot melt adhesive may bedispensed from dispenser 104 and injected into and through aperture 264and into channels 266 and 268, thereby bonding members 260 and 262 ofwindow sash 256 to one another when the molten hot melt adhesive coolsand solidifies.

The members of additional corners 258 of window sash 256 can be bondedin a similar manner with the alignment of dispenser 104 and thecorresponding aperture 264 in one of the members of sash 256 beingachieved by changing the relative positions of dispenser 104 and windowsash 256. This may be achieved by moving dispenser 104, as well as theother components of apparatus 10 mounted on device 300, so as to changethe position of dispenser 104, or by repositioning window sash 256,using various conventional devices known in the art. As a furtheralternative, multiple apparatuses 10, 150, or 200 may be mounted ondevice 300, with each being used to bond the two members of one of thecorners 258 of sash 256 to one another. In this event, the multipleapparatuses 10, 150 or 200 may be manifolded together with respect tothe supply of the solid particles of hot melt adhesive, with thedispenser 104 of each apparatus being aligned with the correspondingaperture 264 of window sash 256.

The apparatus of the present invention, such as apparatus 10, 150 or200, can be used in conjunction with the foregoing methodology to bondmembers of window corners that are not pultruded window corners, i.e.,window corners made from a construction different than a fiberreinforced composite. Additionally, adhesive may also be applied to theabutting surfaces of members 260 and 262.

FIGS. 9 and 10 illustrate another application where the apparatus of thepresent invention, such as apparatus 10, 150 or 200, can be used tocreate a side seam 280 of a filter 290 shown in FIG. 9, where filter 290may be an oil filter for a motor vehicle for example. Filter 290 isconstructed of a filter material 282 that is formed into a plurality ofpleats 284 disposed about the periphery of filter 290, from a flat sheetor block of the filter fabric. The pleated block is then formed into thecylindrical shape shown in FIG. 9, with the ends of the pleated blockdisposed in abutting relationship. The heated manifold 40, hopper 12,pump 86 and dispenser 104 may be mounted to the dedicated automationdevice 300 as illustrated schematically in FIG. 11. Dispenser 104 maythen be aligned with the two ends of filter 290 and seam 280 can beformed, bonding the two ends of the pleated block together, bydispensing the molten hot melt adhesive from dispenser 104 onto one orboth of the two ends of the pleated block. The molten hot melt adhesivemay flow along the abutting surfaces of the two ends. When the moltenhot melt adhesive cools and solidifies, a structurally sound seam, orjoint, is created. A center tube assembly (not shown) may then beinserted in the interior 286 of filter 280. In use, the fluid to befiltered flows through the center tube assembly and radially outwardlythrough a plurality of holes (not shown) formed about the periphery ofthe center tube assembly and then through filter 280.

While the foregoing description has set forth preferred embodiments ofthe present invention in particular detail, it must be understood thatnumerous modifications, substitutions and changes can be undertakenwithout departing from the true spirit and scope of the presentinvention as defined by the ensuing claims. The invention is thereforenot limited to specific embodiments as described, but is only limited asdefined by the following claims.

What is claimed is:
 1. An apparatus for melting thermoplastic material,the apparatus comprising: a heated manifold defining: an upper surfacereceiving particles of thermoplastic material from a hopper; a pluralityof cavities extending downward from the upper surface, each of theplurality of cavities having an inlet and an outlet, the inlets of theplurality of cavities being defined in the upper surface, and theplurality of cavities being spaced apart from one another; a pump supplypassage for receiving molten thermoplastic material from the outlets ofthe plurality of cavities and for supplying the molten thermoplasticmaterial to a pump; and a discharge passage for receiving pressurizedmolten thermoplastic material from the pump, the discharge passage beingin fluid communication with a dispenser; and at least one heatingelement disposed within the heated manifold, the at least one heatingelement transferring heat substantially throughout the heated manifold.2. The apparatus of claim 1, wherein the at least one heating elementcomprises a plurality of heating elements disposed within the heatedmanifold.
 3. The apparatus of claim 1, wherein the at least one heatingelement is at least one electrical resistance heating element.
 4. Theapparatus of claim 1, further comprising a pump mounted to the heatedmanifold, the pump being configured to pressurize the moltenthermoplastic material, and the pump including an inlet in fluidcommunication with the pump supply passage and an outlet in fluidcommunication with the discharge passage.
 5. The apparatus of claim 4,wherein the pump comprises a motor and an output shaft extending fromthe motor.
 6. The apparatus of claim 1, further comprising the hopperthat is external to the heated manifold.
 7. The apparatus of claim 6,wherein the hopper is directly above the plurality of cavities.
 8. Theapparatus of claim 6, wherein the hopper is unheated.
 9. The apparatusof claim 6, wherein the hopper includes an inlet for receiving theparticles of thermoplastic material and an outlet coupled to the heatedmanifold.
 10. The apparatus if claim 9, further comprising a hosecoupled at one end to the inlet of the hopper and at another end to asupply of the particles of thermoplastic material, the hose beingconfigured to transport the particles of thermoplastic material from thesupply to the hopper.
 11. The apparatus of claim 10, wherein the otherend of the hose is operatively coupled to a source of pressured air totransport the particles of thermoplastic material from the supply to thehopper.
 12. The apparatus of claim 11, wherein the hopper comprises avent for exhausting the pressurized air received within the hopper. 13.The apparatus of claim 10, wherein the hose is unheated.
 14. Theapparatus of claim 10, further comprising the supply of the particles ofthermoplastic material.
 15. The apparatus of claim 6, wherein the hopperfurther comprises a level sensor configured to detect the level of theparticles of thermoplastic material in the hopper.
 16. The apparatus ofclaim 1, further comprising a filter within the heated manifold andoverlapping with the discharge passage, the filter for filtering fineparticles within the molten thermoplastic material.
 17. The apparatus ofclaim 1, further comprising a pressure transducer in fluid communicationwith the discharge passage, the pressure transducer being configured tomeasure the pressure of the pressurized molten thermoplastic materialfrom the pump.
 18. The apparatus of claim 1, wherein the thermoplasticmaterial is hot melt adhesive.
 19. The apparatus of claim 15, furthercomprising a controller configured to: receive, from the level sensor,an indication that the level of the particles of thermoplastic materialin the hopper is below a predetermined level; and actuate, in responseto the indication that the level of the particles of thermoplasticmaterial in the hopper is below the predetermined level, a supply of theparticles of thermoplastic material to transport the particles ofthermoplastic material from the supply to the hopper.
 20. The apparatusof claim 1, wherein each of the plurality of cavities iscircumferentially defined within the heated manifold.